Photothermographic material containing a photosensitive metal oxide semiconductor or benzophenone and a free metal generating alkanolamine

ABSTRACT

A photosensitive recording material comprising a metalcontaining amino-alcohol reaction product yielding free metal on heating and in inter-reactive relationship with said product a photosensitive substance, which in photo-exposed state lowers the decomposition temperature of said product. The preferred reaction product is a reaction product of yellow lead(II)oxide and tri-isopropanolamine. Preferred photosensitive substances are photoconductive lead(II)oxide, zinc oxide and titanium(IV)oxide.

United States Patent [191 Heugebaert et a].

]March 20, 1973 [54] PHOTOTHERMOGRAPHIC MATERIAL CONTAINING APHOTOSENSITIVE METAL OXIDE SEMICONDUCTOR OR BENZOPHENONE AND A FREEMETAL GENERATING ALKANOLAMINE inventors: Frans Clement I-Ieugebaert,Kontich; Eric Maria Brinckman, Mortsel,

both of Belgium Assignee: Agfa-Gevaert N.V., Mortsel, Belgi- Filed: May10, 1971 Appl. No.: 142,044

Foreign Application Priority Data May 1 1, 1970 Great Britain..22,682/70 us. Cl. ..96/48 HD, 96/88 Int. Cl ..G03c 1/00, G036 5/32Field of Search ..96/48, 88, 48HD [56] References Cited UNITED STATESPATENTS 1,939,232 12/ 1933 Sheppard et al ..96/ 88 3,259,494 7/ I966Schlein et al. ..96/88 X Primary Examiner-Brown J. Travis AssistantExaminer-Won H. Lowe, Jr. Attorney-William J. Daniel [57] ABSTRACT Thepreferred reaction product is a reaction product of yellow lead(lI)oxideand 'tri-isopropanolamine. Preferred photosensitive substances arephotoconductive lead(ll)oxide, zinc oxide and titanium(lV)oxide.

8 Claims, No Drawings reaction product PHOTOTHERMOGRAPIIIC MATERIAL ICONTAINING A PI-IOTOSENSITIVE METAL OXIDE SEMICONDUCTOR ORBENZOPI'IENONE AND A FREE METAL GENERATING ALKANOLAMINE The presentinvention relates to photothermographic reproduction of information andto recording materials and substances used therefor.

In the US. Pat. specification No. 1,976,302 a method of making aphotographic image has been described, which comprises exposing to alight image a photosensitive layer containing as its primary constituenta salt selected from the group consisting of the silver, lead, mercuryand manganese salts of organic saturated dibasic and tribasic acids,silver formiate, lead formiate and lead thioacetate, whereby a latentimage is formed, and then submitting the layer to heat alone so that avisible image is developed therein.

The materials used in said process have to be kept in the dark untiltheir information-wise exposure. They require a relatively high amountof radiant energy in order to build up the latent image and need arather long duration heating for development.

It is one of the objects of the present invention to provide an improvedphotothermographic recording material in which a visible image is formedin a recording element by the simultaneous action of overall appliedheat and information-wise irradiation-with activating electromagneticradiation.

It is a further object of the present invention to provide a recordingmaterial that obtains print-out imageforming capacity at elevatedtemperatures and maintains its original color at room temperature whenexposed, e.g., to daylight.

Other objects will become apparent from the embodiments describedfurtheron.

According to the basic concept of the present invention an organiccompound yielding free metal on heating is used in interreactiverelationship with a photosensitive substance that by exposure toactivating electromagnetic radiation is capable to decrease thedecomposition temperature of said compound. The photosensitive substancesuited for the purpose of the present invention effects in exposed statepreferably a decrease of the decomposition temperature of the organicmetal compound of at least 20C and more preferably of 50C and-more.

It has been found that an amino-alcohol compound that is capable to forma lead-containing reaction product with lead(II) oxide is a suitablereagent for the production of organometallic compounds that arethermolabile, i.e., splitt off free metal above a critical temperature.

The preparation of such organometallic compounds proceeds preferably byintimately contacting through mixing the amino-alcohol with (l) a finelydivided basic metal oxide, or (2) a metal compound containing the metalof such oxide linked to at least one hydroxyl group, or (3) a metalcompound wherein the metal of said oxide is present in an enolate group,or (4) a metal compound wherein said metal replaces the hydrogen atom(s)of the hydroxyl groups of an element that can form weak acidic,amphoteric or weak basic hydroxides, e.g., derived from the elementsarsenic, antimony, bismuth, thallium and lead.

The reaction conditions are selected such that the decompositiontemperature of the formed metal-containing amino-alcohol reactionproduct is not surpassed. A suitable reaction temperature range for thepreferably used compounds is between room temperature and a temperaturethat is 20C below the decomposition temperature.

The presence of an inert solvent and an intimate mixing of the reagentsas effected by ball-milling or high speed stirring is advantageous forobtaining reproducible results very quickly.

Examples of suitable basic metal oxides are listed in the followingTable under the numbers 1 and 2. An example of a suitablehydroxyl-containing metal compound is compound 8. The'metal compounds 3and 4 are enolate compounds. The compounds 5 and 6 are examples ofcompounds wherein the hydrogen atoms 7 of the hydroxyl groups of anelement that can form weak acidic hydroxides have been replaced by ametal that can form a basic oxide. Compound 7 forms a hydroxy-leadcompound in alkaline conditions.

Preferred amino-alcohol compounds are trialkariolamino compounds. Thealiphatic carbon groups in said compounds have preferably from 2 to 5carbon atoms.

.Very good results are obtained with metal-containing amino-alcoholcompounds having a decomposition temperature above Cand wherein themetal is no stronger electron-donating than zinc, preferably no strongerelectron-donating than lead.

The metal set free from the organometallic compound is preferably fairlystable to aerial oxidation and is, e.g.,' a metal of the classcomprisinglead, copper, silver, mercury, zinc and thallium.

Particularly suited for the purpose of the present invention are thereaction products of triisopropanolamine and one of the compounds listedin the following Table.

Table yellow lead(II) oxide (massicot) red to tan lead(II) oxide(litharge) copper(II) acetylacetonate zinc acetylacetonate mercury(ll)arsenite thallium(lll) arsenite Excellent results have been obtainedwith the reaction product of lead(II) oxide and triisopropanolamine. Ithas the following structural formula:

V 500 ml of trichloroethylene and 50 m] of toluene till the yellow colordisappears. The thus obtained suspension is ready to be mixed with theelected photosensitive decomposition-promoting agent that is capable oflowering the decomposition temperature of theheatdecomposablemetal-containing amino-alcohol compound by absorbingactivating electromagnetic radiation.

Suitable photosensitive agents promoting decomposition can be found inthe class of the photoconductive compounds, e.g., oxygen-containingphotosensitive semiconductor compounds.

Particularly suited for being applied according to the present inventionare inorganic photosensitive semiconductor substances such astitanium(IV) oxide, zinc oxide, yellow lead(ll) oxide, and bismuth(lll)oxide, or mixtures of said substances.

An organic substance that acts as a photosensitive semiconductorcompound promoting the liberation of free metal from the heatedorganometallic compound is benzophenone. Excellent results are obtainedtherewith, e.g., when used in conjunction with the organometallicreaction product of triisopropanolamine and lead(lI) oxide.

In a special embodiment use is made of photosensitive semi-conductorcompound that by itself on exposure to activating electromagneticradiation yields a free metal. This metal preferably is the same as thatset free by the organometallic compound or should have a strongerelectron-donating character.

Such a photosensitive semi-conductor compound is yellow lead(ll) oxide,which is admixture with the thermolysable reaction product oftri-isopropanolamine and yellow lead(ll) oxide produces lead metal onexposure to activating electromagnetic radiation.

The yellow lead(ll) oxide may be replaced advantageously by otherphotosensitive semiconductor compounds such as photoconductive zincoxide and titanium(IV) oxide.

Photoconductive zinc oxide and titanium(IV) oxide are inherentlysensitive to ultra-violet radiation of wavelengths between about 360 nmand 420 nm; photoconductive yellow lead(lI) oxide is inherentlysensitive to radiation of wavelengths between about 360 nm and 460 nm.

The treatment of zinc oxide and titanium(IV) oxide by heating in vacuowill increase the photoresponse. The photoconductivity is raised bydoping, e.g., with aluminium or chromium ions, and/or by dyesensitization.

The state of subdivision of the semiconductor particles is not critical,although very finely divided particles with a specific area as high aspossible are preferred.

ln'general, commercially available photocondu'ctive semiconductormaterials having a particle size between about 0.03 and about 0.5microns are employed. The larger the con-tact area between thephotoactivatable agent promoting decomposition and the thermolysableorganometallic compound, the higher the total photoand heat-sensitivityof the system.

Preferablya mixture of a photosensitive semiconductor compound with athermolysable metal-containing amino-alcohol compound formed in situ isused, since such a composition contains the agent promotingdecomposition and the thermolysable organometallic compound in veryintimately mixed state. However, the

use of said reaction product in a layer being in intimate contact with alayer containing said agent promoting composition is not excluded.

Having in mind the preceding it is clear that the time needed to form avisible image will depend on the in-' tensity of the exposure, theamount of effectively absorbed radiation and heat, the intrinsicphotosensitivity of the semiconductor, the degree of effective contactwith the thermolysable organic compound and its influence on the thermaldecomposition thereof.

The ratio by weight of thermolysable organometallic compound tophotosensitive agent promoting decomposition may vary within wide limitsbut preferably it is larger than 1.

A suitable ratio range of thermolysable compound to photosensitive agentis between 20:1 to 1:2 by weight.

A suitable coating according to the present invention containsapproximately between 1 and 10 g of thermolysable organometalliccompound per sq.m.

For the preparation of the recording material accordingto the presentinvention the thermolysable organo-metallic compound and photosensitiveagent promoting decomposition are applied together to a suitable supportfrom a solution or dispersion in an inert solvent containing a dissolvedfilm-forming binding agent.

As binding agent for the photoand heat-sensitive substances contained inthe recording layer of the present invention all kinds of natural resinsmay be used, e.g., proteins such as gelatin, modified natural resins,e.g., cellulose esters and synthetic resins such as vinyl polymers. Bestresults, however, are obtained with film-forming binding agents thathave a predominantly hydrophobic character, such as polyolefines, e.g.,polyethylene, copolymers of butadiene and styrene, copolymers ofacrylonitrile and butadiene, polyvinyl acetate, polyvinyl chloridecontaining a minor amount of chloro-sulphonyl groups, copolymers ofbutadiene and styrene containing a minor amount of unsaturatedcarboxylic acid such as maleic acid, a reaction product ofpolyethyleneimine and an aliphatic epoxide, and polyethylene containingin its structure a minor amount of carboxyl groups.

Suitable supports for the recording layer are, e.g., paper supports suchas a glassine type paper support,

and resin supports known from silver' halide photography. It is alsopossible to apply the recording com- Example 1 110 g of yellow lead(ll)oxide were ball-milled for 12 h in the presence of 100 g oftri-isopropanolamine, 500

ml of trichloroethylene and 50 ml of toluene till disappearance of theyellow color.

To the ball-milled composition 40 g of photosensitive semiconductivetitanium (IV) oxide and 800 g of 20 percent by weight polyethylenesolution in trichloroethylene were added. Ball-milling was continued forfurther 2 h.

The obtained suspension was spread onto a paper support in a ratio of100 g per sq.m and dried at room temperature.

The obtained recording material was contact-exposed through atransparent original for 60 sec. while it was heated at 90C. Theexposure was carried out with a HPR lamp of 125 W (an ultra-violet lampmarketed by N.V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands)placed at a distance of 5 cm from the recording layer.

A black print-out image having a maximum density of 1.4 in the imageareas and a fog density of 0.1 in the background areas was obtained.

Examples 2-4 Analogous results were obtained by replacing the 40 g oftitanium(IV) oxide by a same amount of one of the following compounds:

photoconductive zinc oxide;

photosensitive lead(ll) oxide (massicot);

benzophenone.

Example 5 l 12 g of yellow lead(ll) oxide were ball-milled for 2 h inthe presence of 100 g of tri-isopropanolamine, 500 ml oftrichloroethylene and 50 ml of toluene till disappearance of the yellowcolor.

49 g of the thus obtained dispersion were ball-milled for further 2 h inthe presence of 41 g of a 20 percent by weight solution of polyethylenein trichloroethylene. Subsequently the obtained mixture was coated on a7 paper base at a coverage of 100 g per sq.m.

After drying, the coated layer was provided with a top-coating appliedfrom a dispersion containing the following ingredients:

titanium(lV) oxide 4 g EPlKOTE-l62 (trade name of Shell Chemicals lnc.for an aliphatic polyepoxide binder) 17 g polyethyleneimine 2 8trichloroethylene 15 g Example 6 112 g of yellow lead(ll) oxide wereball-milled for 2 h in the presence of 100 g of tri-isopropanolamine,500 ml of trichloroethylene and 50 ml of toluene till disappearance ofthe yellow color.

49 g of the thus obtained dispersion were ball-milled for further 2 h inthe presence of 17 g of EPIKOTE-162 (trade name), I g of a mineral waxwith melting point C, 15 I g of trichloroethylene, 2 g ofpolyethyleneimine and 4 g of epichlorhydrine.

The dispersion was coated onto a paper support bearing a whitetitanium(lV) oxide coating having 7 g of TiO per sq.m.

The dried recording material was placed in a vacuum frame in contactwith a metal plate heated at C and contact-exposed for 60 sec. through atransparent silver image negative by means of a 2000 W mercury vaporlamp. A black print-out image with a maximum density 0.94 and a fogdensity 0.15 was obtained.

When the above dispersion was coated onto a paper support that had notbeen provided with a titanium(l V) oxide. pigment coating the sameexposure yielded an image with a maximum density of only 0.23 and a fogdensity of 0. l 3.

We claim:

1. Aphotosensitive recording material comprising an organometallicderivative of an alkanolamine yielding free metal on heating and ininter-reaction relationship with said derivative a photosensitivesubstance which in photo-exposed state lowers the decompositiontemperature of said derivative, said photosensitive substance beingbenzophenone or at least one oxygen-containing inorganic semiconductivecompound of lead, titanium, zinc or bismuth.

2. A photosensitive recording material according to claim 1, wherein thederivative alone is stable up to 100C but above said temperaturedecomposes and yields free metal.

3. A photosensitive recording material according to claim. 1, whereinsaid organometallic derivative is a reaction product of an alkanolamineand a metal compound selectedfrom yellow lead(ll) oxide '(massicot), redlead(ll) oxide (litharge), copper(ll) acetylacetonate, zincacetyl-acetonate, mercury(ll) arsenite, thallium(ll1) arsenite,

and HO-Pb-S-Cl-b-Cllr-OH.

4. A photosensitive recordingmaterial according to claim 3, wherein thereaction product has the following structural formula:

5. A photosensitive recording material according to claim 1, wherein thephotosensitive substance and orsitive substance, which in photo-exposedstate lowers the decomposition temperature of said derivative, andheating said recording material during or after exposure to develop avisible image in the unexposed areas thereof, said photosensitivesubstance being benzophenone or at least one oxygen-containing inorganicsemiconductive compound of lead, titanium, zinc or bismuth.

8. A recording material according to claim 1 wherein the metallic atomsof said organometallic derivative arev of-the same metal as thesemiconductive compound.

2. A photosensitive recording material according to claim 1, wherein thederivative alone is stable up to 100*C but above said temperaturedecomposes and yields free metal.
 3. A photosensitive recording materialaccording to claim 1, wherein said organometallic derivative is areaction product of an alkanolamine and a metal compound selected fromyellow lead(II) oxide (massicot), red lead(II) oxide (litharge),copper(II) acetylacetonate, zinc acetyl-acetonate, mercury(II) arsenite,thallium(III) arsenite, and HO-Pb-S-CH2-CH2-OH.
 4. A photosensitiverecording material according to claim 3, wherein the reaction producthas the following structural formula:
 5. A photosensitive recordingmaterial according to claim 1, wherein the photosensitive substance andorganometallic derivative are used in a same layer in admixture with afilm-forming binding agent.
 6. A photosensitive recording materialaccording to claim 1, wherein the organometallic derivative andphotosensitive substance are present in separate layers that are inintimate contact with each other.
 7. A method of recording informationcomprising the steps of information-wise exposing to activatingelectromagnetic radiation a photosensitive recording material comprisingan organometallic derivative of an alkanolamine yielding free metal onheating and in interreactive relationship with said derivative aphotosensitive substance, which in photo-exposed state lowers thedecomposition temperature of said derivative, and heating said recordingmaterial during or after exposure to develop a visible image in theunexposed areas thereof, said photosensitive substance beingbenzophenone or at least one oxygen-containing inorganic semiconductivecompound of lead, titanium, zinc or bismuth.
 8. A recording materialaccording to claim 1 wherein the metallic atoms of said organometallicderivative are of the same metal as the semiconductive compound.